1. Field of the Invention
The present invention relates to optical fiber ribbons including optical fibers and cables, and more particularly to optical fiber ribbons including one or more optical fibers disposed in a matrix material. Further, the present invention relates to optical fiber ribbons having well balanced ribbon properties desirable for handling optical fiber ribbons during production, splicing operations, and midspan access.
2. Related Art
Optical fiber ribbon is a type of optical fiber cable that has become quite popular for many uses. Unlike conventional loose tube optical cables wherein the 250 micrometer (.mu.m) color-coded optical fibers are placed loosely inside a gel-filled plastic tube, optical fiber ribbons contain a matrix material which fixedly holds a plurality of optical fibers therein. Optical fiber ribbons normally incorporate 250 .mu.m color-coded optical fibers--typically 2-24 optical fibers--which are held together in the form of a flat linear matrix by a suitable ultraviolet (UV) curable encapsulant matrix material. Although different materials can be utilized for the matrix material, the matrix material is most suitably formed from UV curable acrylate based resins which are well known in the fiber optic art. However, a matrix material including a variety of desired handling characteristics such as good heat strip, encapsulation, easy peel, breakout, good fiber geometry and robustness has remained unknown, even though, as discussed below, matrix materials having individual ones of the desirable handling characteristics have been developed. That is, because the properties of the matrix material often affect handling characteristics in different ways, it has been difficult to develop an optical fiber ribbon having optimal handling characteristics.
U.S. Pat. No. 5,761,363 to Mills (Mills) discloses an optical fiber ribbon which is heat strippable and peelable. Although Mills recognizes that adhesion between the matrix material and the optical fibers therein affects peelability, he does not recognize that the properties of the matrix material affect the heat strippability and peelability of the ribbon. Instead, Mills provides an interfacial layer disposed between the outermost layer on each individual optical fiber and the matrix material. In disposing an interfacial layer, Mills adds complexity and cost to the production of an optical fiber ribbon.
U.S. Pat. No. 4,953,945 to Nishimura et al. (Nishimura) discloses an optical fiber tape which allows easy handling in splicing operations and which also has resistance to lateral pressures, thereby reducing the transmission loss due to microbending of the optical fibers in the tape. However, similar to Mills, Nishimura introduces a peelable coating layer between the optical fibers and the matrix material in which they are disposed. Again, like Mills, this arrangement adds complexity and cost to the production of an optical fiber ribbon.
U.S. Pat. No. 5,600,750 to Beasley, Jr. et al. (Beasley) discloses a method for midspan entry of optical ribbon fiber. Beasley notes that the success of his midspan entry method is dependent on the properties of the matrix material used in the optical ribbon fiber. In particular, Beasley notes that the midspan access is dependent on the property of peel strength, or adhesion, between the matrix material and the optical fibers therein, and on the sheer strength of the matrix material. However, Beasley does not disclose a matrix material having the desired properties of good heat strip, encapsulation, good fiber geometry and robustness.
In sum, the related art does not provide--in an optical fiber ribbon--a matrix material which includes a variety of desired handling characteristics such as good heat strip, encapsulation, easy peel, breakout, good fiber (geometry and robustness. Further, the related art discussed above does not provide for even individual ones of the desired handling characteristics in an easy to manufacture and cost-effective manner.